(Advisory: Note language in paragraph 11) By Andrew Hay (Reuters) - The painful history of blackface in America was highlighted this week as two top Virginia Democrats came under fire after admitting to having blackened their faces to resemble African-Americans while in college in the 1980s. While the practice is less common than it was decades ago, African-American scholars say it persists in some corners as evidence of racism. Apologies by Virginia Governor Ralph Northam and Attorney General Mark Herring followed blackface appearances by celebrities such as actor Billy Crystal and late-night talk show host Jimmy Fallon in recent years.